Synonyms for Colossal:

adj.

all (adjective)
prodigious, stupendous.
large (adjective)
extensive, soaring, mammoth, tremendous, grandiose, enormous, copious, massive, roomy, immense, prodigious, generous, impressive, giant, gargantuan, grand, ample, spacious, princely, vast, lofty, humongous, baggy, expansive, magnificent, great, comprehensive, towering, gigantic, large, huge, cavernous, capacious, big, bulky, voluminous, sizable, majestic, awesome, elephantine.
very large (adjective)
jumbo, monstrous, humongous, gargantuan, elephantine, immense, cyclopean, vast, enormous, titanic, gigantic, mountainous, mammoth, huge, giant.

n.

high, study at enormous. monster, Brobdingnagian, Gigantesque, jumbo, Bunyanesque, mountainous, cyclopean, whopping, behemoth, walloping, Pythonic, titanic, monstrous, monumental, heroic, Massy, mighty, mastodonic, herculean. colossal (noun)
large, big, prodigious, stupendous.

Other synonyms:

titanic, Pythonic, Gigantesque, mastodonic, cyclopean, Brobdingnagian, walloping, Bunyanesque, Massy. monumental, herculean, mountainous, whopping. heroic, monstrous. mighty. monster. tall
high.
Other relevant words:
mighty, mastodonic, monstrous, whopping, monumental, behemoth, jumbo, Brobdingnagian, titanic, herculean, Massy, stupendous, Pythonic, mountainous, high, cyclopean, monster, walloping, Gigantesque, Bunyanesque, heroic.

Usage examples for colossal

  1. And thus through the whole of the two memorable campaigns made by Alexander in France, he never failed to give his master the most accurate pictures of the country, and an interior view of its politics; urging above all the absolute necessity of providing much more liberal supplies for the colossal adventure in which he was engaged. – History of the United Netherlands, 1592-94 by John Lothrop Motley
  2. At one side, upon a lofty column of granite, was a colossal head of the blackest marble, which she perceived, by the crown of wheat- ears that encircled the brow, represented the great Egyptian goddess. – The Last Days of Pompeii by Edward George Bulwer-Lytton
  3. Throw this immeasurable pile of war- waste and colossal suffering into the scales of thoughtful contemplation, then heap into it as a counter- weight the blessings that have accrued, and the effect upon our minds must necessarily be to lead us to become more hopeful and less ungrateful. – Over the Top With the Third Australian Division by G. P. Cuttriss